Abstract: A portable device for accurately measuring acoustic velocities in solids. This portable hand-held device (100) uses dual receiving transducer tips (110, 112) to allow differential measurement of acoustic velocity in a solid. A body having a handle uses a transmitting transducer tip (108) to transmit acoustic energy to a solid. The first receiving transducer tip (110) is used in conjunction with a second receiving transducer tip (112) mounted on the body a fixed distance from the first (110). The device (100) uses the differences in the time of arrival of the wavefront at the first and second transducers to calculate the acoustic velocity in a given solid. This differential measurement method reduces acoustic velocity measurement inaccuracies.

Abstract: The shear velocity of a region of an earth formation may be determined by a logging tool insertable in a wellbore penetrating the formation which includes plural transducers for generating compressional waves for transmission through the formation as shear wave between the signal generating transducers and an array of signal receiving transducers spaced from the signal generating transducers. The transducers may be plural in number and arranged to effect impingement of the compressional wave on the borehole wall at an angle of incidence preferably in the range of 35.degree. to 75.degree. to a normal to the wall surface. The transducer array is controlled so that a significant portion of the compressional wave energy transmitted through liquid in the wellbore is converted to shear waves at the wellbore wall, which shear waves constructively interfere to develop a torsional wave propagating along the wellbore between the transducers and the receiver elements.